486 BULLETIN G.*], UNITED STATES NATIONAL MUSEUM. 



grooves more or less evanescent in l)asal half and feebly defined 

 apically, very shallow but rather smooth. 



l*rotibia^ distinctly compressed, especially along the inner side; 

 external border arcuate in basal half, thence straight and with a tarsal 

 groove, that evenly and gradually widens to the articular cavity 

 with which it is continuous; the anterior margin of the groove is 

 rather smooth, the posterior more or less denticulate; the anterior 

 and posterior sides of the articular cavities are feebly dilated. Le- 

 Conte says that the apical angle is produced, but I do not see that it 

 is in the least so. In the male of costatus the protibia? are briefly and 

 very abruptly constricted at base so that a right angle is formed : the 

 tibiae thence to apex quite even in width, as a Avhole slightly arcuate, 

 each internal edge very broadly and feebly sinuate. 



The meso- and metatibise are slender, straight, gradually and feebly 

 increasing in size to apex, where they are somewhat dilated, circular 

 in transverse section, and more or less grooved or flattened externally 

 for the tarsi ; articular cavities closed. 



The protuberant prosternum is very obvious in costatK,^^ less so in 

 tuherculatiis, in each it is deeply grooved around the anterior border 

 of the acetabula ; in tuherculatus the anterior margin is distinctly 

 deflexecl. 



Distribution. — Confined as far as known to the arid regions of 

 eastern California and western Nevada, northward into Idaho. 



The two known species may be separated as follows: 



Pronotum crihratoly ])niK'tate rostntus. 



Prouotum tuberculate , tuherculatus. 



The synopsis of genital characters may be formulated as follows: 



Superior pudendal membrane long, reaching to the apical fourth 



of the dorsal plate , costatus. 



Superior pudendal nK'nil)rane shorter, reaching to a])ical third tubcrculutus. 



TROGLODERUS COSTATUS LeConte. 



TrogUtdcnts coslatus, LkContk, N. Auier. Entomologist. I. No. 1. .July, 

 1871), p. '.i, pi. I, fig. 3. 



Elongate, oblong-oval, opaque, dirty black, integuments dense; 

 thorax cribrately punctate; elytral costa> acutely elevated. 



Head less than twice as wide as long, feebly convex, more or less 

 irregularly impressed, frontal suture not evident, but indicated by 

 the abrupt termination of the fi'ontal impression, ;it times slightly 

 elevated; coarsely and conliuently cribrate, the punctures at times 

 more or less corroded. 



Antenna' short, scarcely reaching l)eyond the middle of the pro- 

 thorax, somewhat clavate. I'ccljly compressed, second joint nearly one- 

 half as long as the third and not quite as long as wide, third joint 

 about equal to the next two taken together, fourth the least hmger 



